JP5125098B2 - Manufacturing method of nitride semiconductor free-standing substrate - Google Patents

Abstract

The present invention provides a method for manufacturing a nitride semiconductor self-supporting substrate and a nitride semiconductor self-supporting substrate manufactured by this manufacturing method, the method including at least: a step of preparing a nitride semiconductor self-supporting substrate serving as a seed substrate; a step of epitaxially growing the same type of nitride semiconductor as the seed substrate on the seed substrate; and a step of slicing an epitaxially grown substrate subjected to the epitaxial growth into two pieces in parallel to an epitaxial growth surface. As a result, there is provided a method for manufacturing a large-diameter nitride semiconductor self-supporting substrate having an excellent crystal quality and small warp with good productivity at a low cost, etc.

Description

  The present invention relates to a group III nitride semiconductor free-standing substrate such as GaN and a method for manufacturing the same.

  Group III nitride compound semiconductors (gallium nitride (GaN), indium gallium nitride (InGaN), gallium aluminum nitride (GaAlN), etc .; hereinafter also simply referred to as nitride semiconductors) have recently become blue, ultraviolet light emitting diodes (LEDs), It has begun to play an important role as a material for laser diodes (LD). In addition to the optical elements, nitride semiconductors have good heat resistance and environmental resistance, or good high-frequency characteristics. Therefore, electronic devices that take advantage of this feature are being actively developed.

However, nitride semiconductors are difficult to grow bulk crystals, and GaN free-standing substrates are only used in limited applications such as laser diodes where cost is not an issue. A substrate for GaN growth that is currently in wide use is a sapphire (Al ₂ O ₃ ) substrate, and generally used is a method of epitaxially growing GaN on a single crystal sapphire substrate by a metal organic chemical vapor deposition method (MOVPE method) or the like. It has been.

  In this case, since the sapphire substrate has a lattice constant different from that of GaN, a single crystal film cannot be grown by directly epitaxially growing GaN on the sapphire substrate. For this reason, a method is proposed in which an AlN or GaN buffer layer is once grown on a sapphire substrate at a low temperature, and lattice distortion is relaxed by the low temperature growth buffer layer, and then GaN is grown on the buffer layer. (Patent Document 1).

However, even in the growth of GaN using this low-temperature growth buffer layer, there is a problem that warpage occurs in the substrate after epitaxial growth due to the difference in thermal expansion coefficient between the sapphire substrate and GaN, leading to cracks and cracks.
Further, the warpage of the substrate after the epitaxial growth becomes a serious problem because the exposure state of the fine pattern in photolithography becomes uneven.
In addition, in blue and ultraviolet LEDs for illumination that are expected to be put to practical use in the future, it is necessary to cause the LED to emit light with high luminance at a high current density. From the viewpoint of luminous efficiency and lifetime, the dislocation density of the GaN light emitting layer is low. A low-priced GaN free-standing substrate with good thermal conductivity to the substrate is desired.
As described above, a method for growing a GaN free-standing substrate having excellent crystallinity and productivity is desired, but there is still no satisfactory solution.

  In order to solve such a problem, an attempt has been made to obtain a GaN free-standing substrate by removing the sapphire substrate by a method such as etching or grinding from a GaN epitaxial growth substrate that is thickly grown on the sapphire substrate. If a GaN free-standing substrate is obtained, various problems caused by the difference in lattice constant and the difference in thermal expansion coefficient in the epitaxial growth of the light emitting layer formation can be solved.

  However, when the sapphire substrate is removed, the internal strain of the GaN epitaxial layer due to the difference in thermal expansion coefficient between sapphire and GaN is locally released, resulting in increased warpage of the GaN substrate and cracking of the substrate. Remains. An attempt has been made to put into practical use a method in which GaN is grown thickly on a sapphire substrate by HVPE (hydride vapor phase epitaxy), and then only a GaN layer is peeled off by irradiation with a laser pulse ( For example, Non-Patent Document 1) has a problem that the substrate is easily cracked in the process of peeling, and there is a problem that complicated processing is required to obtain a large GaN substrate with good reproducibility.

Further, a method for growing GaN using a single crystal of LiAlO ₂ or ZnO having a lattice constant closer to that of GaN instead of a sapphire substrate has been proposed. When these substrates are used, it is relatively easy to peel off the substrate, but it must be heteroepitaxial growth, and a buffer layer is necessary, and due to differences in the growth temperature and melting point of the substrate, There is a problem in putting a GaN substrate excellent in crystallinity into practical use.

Also, a mask such as Si ₃ N ₄ having a window is formed on the GaAs substrate, a low temperature buffer layer is formed, and then lateral epitaxial growth is performed by the HVPE method to form a low dislocation density epitaxial layer, and the GaAs substrate is etched. A method of obtaining a GaN free-standing substrate by removing the substrate by using a method such as that described above (Patent Documents 2 and 3). However, this method requires a step of forming a Si ₃ N ₄ mask having a window, a step of forming a low-temperature buffer layer, and the like. In addition, there is a problem that a large warp occurs in the GaN free-standing substrate.

  In addition, since the HVPE method enables GaN epitaxial growth at a relatively high speed, recently, an ultra-thick film of about 1 cm to 10 cm or more is grown on a Boolean (GaN) free-standing substrate using its characteristics. Attempts to obtain a large number of substrates (slice substrates) by slicing the single crystal ingot formed in this way, and to obtain a large number of free-standing GaN substrates by polishing the slice surface of the slice substrate (hereinafter referred to as the Boolean method) (See, for example, Patent Documents 2 and 3). However, with this method, it has been difficult to stably obtain a GaN free-standing substrate with high crystal quality.

Japanese Patent Laid-Open No. 61-188983 Japanese Patent Laid-Open No. 2000-12900 JP 2000-22212 A Jpn. J. et al. Appl. Phys. Vol. 38 (1999) pt. 2, no. 3A, L217-219

  The present invention has been made in view of such problems, and its main object is to provide a method for manufacturing a large-diameter nitride semiconductor free-standing substrate with excellent crystal quality and low warpage with high productivity and low cost. To do.

The present invention has been made to solve the above problems, and at least a step of preparing a nitride semiconductor free-standing substrate to be a seed substrate, and epitaxial growth of a nitride semiconductor of the same type as the seed substrate on the seed substrate And a step of slicing the epitaxially grown substrate on which the epitaxial growth has been performed in parallel with the epitaxial growth surface to divide it into two, to produce two nitride semiconductor free-standing substrates from one seed substrate that provides a method of manufacture of a nitride semiconductor free-standing substrate according to.

  If the nitride semiconductor free-standing substrate manufacturing method includes such steps and manufactures two nitride semiconductor free-standing substrates from one seed substrate, the nitride semiconductor free-standing substrate to be a seed substrate Since this is homoepitaxial growth in which the same kind of crystal is epitaxially grown, the problem of warping, distortion and cracking does not occur as in the case of heteroepitaxial growth, and the dislocation density of the epitaxial layer can be kept low. As a result, the crystallinity of the product nitride semiconductor free-standing substrate obtained from the epitaxial layer side by the two-division slice can be made high quality.

Moreover, there is no complicated process such as forming a mask having a complicated shape using different materials, and a nitride semiconductor free-standing substrate can be manufactured with high productivity and low cost.
In addition, since the ultra-thick film is not epitaxially grown as in the conventional Boolean method, only the film thickness sufficient to perform the two-division slice is epitaxially grown, so that the epitaxial growth surface during the epitaxial growth can be easily managed. Crystal quality can be easily maintained high.

In this case, it is not preferable to use as the seed substrate again nitride semiconductor free-standing substrate produced by the production method of the nitride semiconductor free-standing substrate.
Thus, if the nitride semiconductor free-standing substrate manufactured by the above-described nitride semiconductor free-standing substrate manufacturing method is used again as a seed substrate, the nitride semiconductor free-standing substrate with high crystal quality obtained at low cost can be used again as a seed substrate. Since it is used, it is possible to obtain a high-quality nitride semiconductor free-standing substrate while keeping the manufacturing cost low.

Further, the seed substrate nitride semiconductor free-standing substrate comprising a ready plurality, wherein the epitaxial growth, in the same chamber, rather preferably be carried out simultaneously on the plurality of seed substrates, the plurality of species the nitride semiconductor free-standing substrate comprising a substrate, especially not preferable be eight or more.
In this way, if a plurality of nitride semiconductor free-standing substrates to be seed substrates, in particular, 8 or more are prepared, and epitaxial growth is simultaneously performed on the plurality of seed substrates in the same chamber, productivity can be improved. It can be significantly improved. Further, in the present invention, since the ultra-thick film is not epitaxially grown as in the conventional boule method, it is easy to manage the gas flow and the like on the growth surface. In this way, the epitaxial growth is performed on a plurality of seed substrates. However, it is easy to maintain the crystallinity of the epitaxial layer.

Moreover, it is not preferable to polish the slice plane of the slice to bisected epitaxial growth substrate.
Thus, by polishing the slice surface of the epitaxially grown substrate that has been sliced and divided into two, the flatness of the nitride semiconductor free-standing substrate can be improved.

Moreover, it is not preferable to perform the epitaxial growth by the HVPE method.
Thus, if epitaxial growth is performed by the HVPE method, epitaxial growth can be performed at high speed. Therefore, a nitride semiconductor free-standing substrate can be manufactured with high productivity.

Moreover, it is not preferable that the thickness of the epitaxial layer and 1mm or less to form in the epitaxial growth step.
As described above, if the thickness of the epitaxial layer formed in the epitaxial growth process is 1 mm or less, the film thickness is much thinner than that of the conventional boule method. High crystal quality can be maintained.

Further, a nitride semiconductor free-standing substrate of the nitride semiconductor free-standing substrate and the manufacturing becomes the seed substrate Ru can be a GaN free-standing substrate.
Thus, if the nitride semiconductor free-standing substrate to be a seed substrate and the nitride semiconductor free-standing substrate to be manufactured are GaN free-standing substrates, a GaN free-standing substrate with high crystal quality can be manufactured and used for various device applications. be able to.

Further, the seed substrate to become a nitride semiconductor free-standing substrate, and a diameter of 37.5mm or more, is 250μm or more in thickness, have preferably be those warp value is 35μm or less.
As described above, if the nitride semiconductor free-standing substrate serving as the seed substrate has a diameter of 37.5 mm or more, a thickness of 250 μm or more, and a warp value of 35 μm or less, the epitaxial layer can be equivalent. Diameter and flatness can be used. As a result, the product nitride semiconductor free-standing substrate obtained from the epitaxial layer side can also be a large-diameter high-quality nitride semiconductor free-standing substrate having comparable diameter and flatness.

Further, a nitride semiconductor free-standing substrate serving as the seed substrate, it is not preferable that as threading dislocation density of 5 × 10 7 ^/ cm ² or less.
In this way, if the nitride semiconductor free-standing substrate serving as the seed substrate has a threading dislocation density of 5 × 10 ⁷ / cm ² or less, the dislocation of the epitaxial layer can be suppressed to the same level, and the epitaxial layer side The dislocation of the product nitride semiconductor free-standing substrate obtained from the above can be suppressed to the same extent.

Further, after said epitaxial growth step, the before slicing step, the epitaxial growth has is preferable to form the groove to induce tools to both slicing perform chamfering the peripheral portion of the substrate.
In this way, after the epitaxial growth step, before the slicing step, if a groove for guiding a tool (inner peripheral blade, wire, etc.) for chamfering and slicing the peripheral portion of the epitaxial growth substrate is formed, It is possible to prevent cracks and chips at the periphery of the substrate during the slicing process, and it is possible to control the thickness of the substrate after slicing (slice substrate) with high accuracy and improve flatness.

The slicing step can be performed using an inner peripheral blade having a blade thickness of 250 μm or less, a single wire saw having a wire diameter of 200 μm or less, or a single blade saw having a blade thickness of 250 μm or less. The
Thus, if the slicing step is performed using an inner peripheral blade or a single blade saw, high parallelism can be ensured on the slicing surface. Further, if an inner peripheral blade or a single blade saw having a blade thickness of 250 μm or less is used, the cutting allowance by slicing can be reduced, and the loss of material can be reduced. Further, if the slicing step is performed using a single wire saw having a wire diameter of 200 μm or less, the cutting allowance by slicing can be further reduced, and the loss of material can be further reduced.

In the slicing step, a plurality of the epitaxial growth substrates are stacked using a multi-wire saw having a wire diameter of 200 μm or less, or a multi-blade saw having a blade thickness of 250 μm or less. Ru can also be carried out by slicing at the same time.
In this way, a plurality of epitaxial growth substrates are stacked by stacking a plurality of epitaxial growth substrates using a multi-wire saw having a wire diameter of 200 μm or less, or a multi-blade saw having a blade thickness of 250 μm or less. If slicing is performed simultaneously, a plurality of epitaxial growth substrates are sliced at the same time, so that productivity can be improved.

Further, the present invention is that provides a nitride semiconductor free-standing substrate, characterized in that it is manufactured by the method of any of a nitride semiconductor single crystal substrate described above.
Thus, a nitride semiconductor free-standing substrate manufactured by any one of the above-described methods for manufacturing a nitride semiconductor single-crystal substrate is a nitride semiconductor free-standing substrate having high crystal quality.

In this case, the diameter is not less than 37.5 mm, and a thickness of 250μm or more, Ru can be assumed warp value is 35μm or less.
As described above, a nitride semiconductor free-standing substrate having a diameter of 37.5 mm or more, a thickness of 250 μm or more, and a warp value of 35 μm or less has a large diameter and high flatness. It can be used as a substrate for various device applications.

Moreover, it is not preferable threading dislocation density of 5 × ¹⁰ 7 / cm ² or less.
Thus, a nitride semiconductor free-standing substrate having a threading dislocation density of 5 × 10 ⁷ / cm ² or less is a nitride semiconductor free-standing substrate having sufficiently high crystal quality.

  With the method for manufacturing a nitride semiconductor free-standing substrate according to the present invention, a large-diameter nitride semiconductor free-standing substrate with excellent crystal quality and small warp can be manufactured with high productivity and low cost.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.
As described above, as a method of manufacturing a GaN free-standing substrate, the method of forming a mask on a GaAs substrate or the like and performing lateral epitaxial growth has a problem that a very complicated process is required. Therefore, it led to high cost. Further, when GaN is grown on a heterogeneous substrate by the HVPE method or the like like this method, the epitaxial growth substrate is greatly warped due to the difference in the lattice constant and the thermal expansion coefficient between the seed substrate and the epitaxial layer. As a result, even after the substrate is removed by lift-off, a large warp remains in the product GaN free-standing substrate, and it is extremely difficult to correct this warp in the subsequent processing steps, which has been a problem in the device manufacturing process.

  On the other hand, the Boolean method has an advantage that a GaN single crystal can be used for the substrate. However, when thick epitaxial growth is performed, if foreign matter adheres to the surface of the epitaxial layer, large protrusions are formed, and crystal defects and polycrystal growth occur in those portions. In order to avoid the adhesion of foreign substances, it is advantageous to face the growth surface downward, but a new problem arises that it becomes difficult to attach the substrate to the holder. Thus, it is necessary to prevent adhesion of foreign substances that are the source of crystal defects over a long period of time, and the epitaxial growth surface is kept constant over a long period of time during the epitaxial growth of an ultra-thick film that is performed for a long time. For example, it is extremely difficult to obtain a high-quality nitride semiconductor free-standing substrate with high productivity and yield. Further, since fine adjustment is necessary for management of gas flow and the like on the growth surface, the number of boules to be manufactured in the same chamber (reaction tube) cannot be increased, and productivity cannot be increased.

  Therefore, the present inventors have conducted intensive experiments and studies on a method for manufacturing a nitride semiconductor free-standing substrate at low cost and with high productivity. As a result, if a nitride semiconductor free-standing substrate is used as a seed substrate, homoepitaxially grown to a predetermined thickness, and the obtained nitride semiconductor epitaxially grown substrate is sliced into two, nitride with high productivity and low cost and high crystal quality It has been conceived that the number of semiconductor free-standing substrates can be obtained twice as many as the number of seed crystals. In addition, the nitride semiconductor free-standing substrate manufactured as described above can be used again as a seed substrate, and the cost of the entire manufacturing cycle can be reduced, and the present invention has been completed.

The present invention can be applied to various group III nitride semiconductors (group III metal nitrides such as aluminum, gallium, and indium, or mixed crystals thereof). An example of the case will be described.
FIG. 1 is a process diagram showing an example of a method for manufacturing a nitride semiconductor free-standing substrate according to the present invention.

First, a nitride semiconductor free-standing substrate is prepared as a seed substrate 101 (step a).
The seed substrate 101 is the same type as the nitride semiconductor free-standing substrate that is finally manufactured. The nitride semiconductor free-standing substrate to be the seed substrate may be manufactured by any manufacturing method, and for example, may be manufactured by a manufacturing method described in Patent Documents 2, 3 and the like. However, it is preferable to use a nitride semiconductor free-standing substrate that satisfies the following conditions.

First, the threading dislocation density is preferably as low as possible, particularly 5 × 10 ⁷ / cm ² or less, more preferably 1 × 10 ⁷ / cm ² or less. The present invention is homoepitaxial growth in which the same kind of nitride semiconductor is grown on a seed substrate. Since the epitaxial layer is affected by the crystal quality of the seed substrate, it is preferable to use a seed substrate having a low threading dislocation density.

  Further, the diameter of the seed substrate is preferably 37.5 mm (1.5 inches) or more, and more preferably 50 mm (2 inches) or more. In order to manufacture a device such as an LED industrially at low cost, a device having a larger substrate area is preferable. In addition, the size of the nitride semiconductor free-standing substrate that is finally produced is affected by the size of the seed substrate. Therefore, such a large-diameter seed substrate is used.

  Moreover, it is preferable that the warp value at the time of 50 mm (2 inch) diameter conversion is 35 micrometers or less. Since the present invention is homoepitaxy, unlike the case of heteroepitaxy, the epitaxially grown substrate after bisection can be warped to the same extent, and the finally produced nitride semiconductor free-standing substrate is also warped to the same extent. It becomes possible to suppress. If warpage of the substrate can be suppressed to a small level, for example, photolithography in the device manufacturing process is not hindered, and the process can be proceeded stably.

  Moreover, it is preferable that thickness is 250 micrometers or more. With such a thickness, the strength and resistance to deflection are sufficient, and the seed substrate 101 side can be sliced with sufficient strength in the two-division slicing step of step d described later.

Next, a nitride semiconductor of the same type as the seed substrate 101 is epitaxially grown on the seed substrate 101 to form an epitaxial layer 102, thereby forming an epitaxial growth substrate 103 (step b).
FIG. 2 shows a vertical type HVPE apparatus as an example of an epitaxial growth apparatus used in the present invention.
The HVPE apparatus 1 includes a group III metal compound generation tube 8 that generates a group III metal compound inside a vertical reaction tube (chamber) 2. The group III metal compound production tube 8 is configured as follows. A group III metal boat 6 loaded with a group III metal, a reaction gas introduction pipe 4 for introducing hydrogen chloride as a carrier gas, for example, as a reaction gas, and a rectification for adjusting the flow of the generated group III metal compound gas A plate 10, a dilution gas introduction pipe 5 for introducing a dilution gas for adjusting the flow rate of the generated group III metal compound gas, and a group III metal compound blowing pipe 11 for blowing out the group III metal compound gas are provided. The group III metal compound production tube 8 is heated by the first heater 7. When manufacturing a nitride semiconductor free-standing substrate containing a plurality of group III metal elements, the ratio of the mixture of these metals may be adjusted and mounted on the raw material group III metal boat 6.

  The HVPE apparatus 1 further includes an ammonia introduction tube 3 for introducing ammonia, a rotatable susceptor 13 on which the seed substrate 101 is placed, and an internal protective tube for preventing the reactant from being deposited inside the vertical reaction tube 2. 14, a gas discharge pipe 15 for discharging various gases, a second heater 9 for heating the substrate, and the like.

Using the HVPE apparatus 1 having such a structure, homoepitaxial growth of a nitride semiconductor is performed as follows.
First, the raw material group III metal mounted on the raw material group III metal boat 6 is heated to, for example, 800 to 850 ° C. by the first heater 7. A reaction gas such as hydrogen chloride is blown from the reaction gas introduction tube 4 to the molten raw material group III metal (for example, gallium) and reacted to cause a group III metal compound gas (III metal is gallium and the reaction gas is hydrogen chloride). In this case, gallium chloride) is produced.
The generated group III metal compound gas passes through the rectifying plate 10 and is blown from the group III metal compound blowing tube 11 onto the seed substrate 101 mounted on the rotating susceptor 13. The flow rate of the group III metal compound gas can be adjusted by controlling the flow rate of the dilution gas (hydrogen, nitrogen, etc.) introduced by the dilution gas introduction pipe 5. The seed substrate 101 is heated by the second heater 9, and the group III metal compound gas reacts with the ammonia introduced from the ammonia introduction tube 3, and the epitaxial layer 102 of the group III nitride semiconductor is epitaxially grown on the seed substrate 101. To do.

  In the method for manufacturing a nitride semiconductor free-standing substrate according to the present invention, since the fluctuation of the epitaxial growth surface is small as compared with the boule method, the film thickness can be kept constant with respect to the gas flow for supplying the epitaxial growth gas. The distribution is not deteriorated. It is not necessary to move the substrate during epitaxial growth as in the boule formation and keep the growth interface constant with respect to the gas flow, and there is an advantage that the apparatus is not complicated.

It is desirable to keep the thickness of the epitaxial layer 102 to the minimum necessary. The thickness of this epitaxial layer 102 is preferably 1 mm or less at the maximum, although it depends on the thickness of the nitride semiconductor free-standing substrate to be finally obtained from the epitaxial layer 102 side.
With such a thickness, the epitaxial layer can be grown only to the minimum necessary thickness. Therefore, even if a large number of seed substrates 101 are charged simultaneously with a normal HVPE apparatus, the growth surface has an influence on the gas flow. Epitaxial growth can be performed within a range that is not greatly affected (that is, the thickness distribution in the substrate is not deteriorated), and a high-quality epitaxial layer can be formed with high productivity. In this respect, the nitride semiconductor free-standing substrate manufacturing method of the present invention is superior to the conventional boule method.

  Epitaxial growth in the present invention is not limited to the above HVPE method, but in the present invention in which it is necessary to form a slightly thick nitride semiconductor epitaxial layer of about 1 mm or less, if the HVPE method is used, For example, it is preferable because the nitride semiconductor can be epitaxially grown at a high speed of 100 μm / hour or more.

  Further, in the present invention, it is not necessary to perform the epitaxial growth of an ultra-thick film having a thickness of about 1 cm to 10 cm or more as in the above-described boule method, so that the management of the gas flow and the like on the growth surface is easy. Even if epitaxial growth is performed on a single seed substrate, the crystal quality of the epitaxial layer can be easily maintained. Therefore, a plurality of seed substrates 101 can be prepared and epitaxial growth can be simultaneously performed on the plurality of seed substrates 101 in the same chamber 2. In this way, productivity can be improved. . In particular, 8 or more substrates can be processed simultaneously, and 20 or more substrates can be processed simultaneously.

In homoepitaxial growth of GaN, even if the seed substrate 101 having a relatively low dislocation density is used, in the current epitaxial growth by the HVPE method, the dislocation density increases to about 5 × 10 ⁸ / cm ^{2 at the} initial stage of growth. As it progresses, the dislocation density decreases, and the dislocation density becomes 5 × 10 ⁷ / cm ² or less at the stage of growing about 400 to 800 μm. In the method for manufacturing a nitride semiconductor free-standing substrate according to the present invention, if a region having an epitaxial growth thickness of about 0 to 300 μm where the dislocation density is increased corresponds to a region that is removed as a cutting margin in a two-division slice process described later. There is also an advantage that the crystal quality of the product nitride semiconductor free-standing substrate obtained from the epitaxial layer side 102 can be secured to about 5 × 10 ⁷ / cm ² or less.

  In addition, since the nitride semiconductor free-standing substrate manufactured according to the method of the present invention is manufactured by homoepitaxial growth, the internal strain of the epitaxial growth substrate 103 is much smaller than that in the case of heteroepitaxial growth. Therefore, the curvature (warp) of the substrate becomes a problem by managing the V-III ratio (ratio of nitrogen atom to group III metal atom) during epitaxial growth and correcting the warp of the seed substrate 101 in the slicing process described later. No longer.

Next, a groove for guiding a tool for slicing and slicing the peripheral portion of the epitaxial growth substrate 103 may be formed (step c). That is, it is effective to perform chamfering and groove formation with a diamond wheel or the like before the two-division slicing step of step d.
By performing chamfering and groove formation in this way, in the two-division slicing step of step d, the outer peripheral surface of the substrate can be more easily made perpendicular to the direction of slicing, and the blade or wire can be cut into a predetermined shape. It is possible to prevent deviation from the surface. As a result, the thickness variation and local curvature (warp) of the substrate (slice substrate) after the two-division slice can be further reduced. Further, the substrate is required to have a predetermined shape and diameter, and it is possible to prevent cracking and chipping at the outer peripheral portion during handling of the nitride semiconductor free-standing substrate after completion of slicing. Specifically, for example, a chamfer 103a and a groove 103b as shown in FIG. 3B are formed in the peripheral portion of the epitaxial growth substrate 103 immediately after the epitaxial growth having a shape as shown in FIG. The overall shape is preferably W-shaped. If it is such a chamfered shape, as shown in FIG. 3C, after the two slices are sliced in step d, both of the two nitride semiconductor free-standing substrates 104 are chamfered. During the handling of the nitride semiconductor free-standing substrate 104 after completion of slicing, it is possible to prevent cracking and chipping at the outer peripheral portion. In addition, you may chamfer further after a slice process.

Next, the epitaxially grown substrate 103 on which the above-described epitaxial growth has been performed is sliced in parallel with the epitaxial growth surface and divided into two to form two nitride semiconductor free-standing substrates (sliced substrates) 104. (Step d).
This two-division slice can be performed by using, for example, an inner peripheral blade 34 electrodeposited with diamond as shown in FIG. First, the epitaxial growth substrate 103 is adsorbed (adhered) to the ingot holder 31 via the wafer stage 32. Various methods such as a vacuum chuck can be used for adsorbing (adhering) the epitaxial growth substrate 103 to the wafer stage 32 and may be appropriately selected. However, when the epitaxial growth substrate 103 is slightly warped, for example, If the wafer 38 is bonded to the wafer stage 32 with the wax 38 as shown in FIG. 6, it is possible to prevent the substrate from being damaged by slight warping. Note that the slice surface does not have to be matched to the wafer shape and may be sliced horizontally.

  In addition, in order to prevent the substrate from cracking in the second half of the slice, it is desirable to adhere the contact plate 35 to the substrate. The pad 35 is preferably attached to the orientation flat side, and the slice is preferably started from the opposite side. As the inner peripheral blade 34 at this time, if a blade that is as thin as possible (for example, a blade thickness of 250 μm or less) is used as long as the tension of the blade that can secure parallelism can be secured, the cutting allowance (kerfloss) can be reduced. It is preferable because the epitaxial growth thickness can be reduced and the loss of material can be reduced. Further, during the slicing, the cutting coolant is supplied from the cutting coolant supply means 36 to the slicing portion of the inner peripheral blade 34.

In addition, the above-mentioned two-division slice can be performed as follows using a wire saw 51 in which diamond is electrodeposited as shown in FIG. First, the wafer stage 32 is adhered (adsorbed) with wax or the like, and the contact plate 35 is attached to the orientation flat side. Then, the epitaxial growth substrate 103 is sliced into two while the cutting coolant is supplied from the cutting coolant supply means 36 to the wire saw 51.
According to this method, since the wire is generally thinner than the thickness of the inner peripheral blade, the cutting allowance by slicing can be further reduced, and the loss of material can be reduced. In addition, it is preferable to use a thin wire as long as the tension of the wire that can ensure the parallelism in the slice can be secured and maintained as in the case of the inner peripheral blade, and the diameter of the wire is, for example, 200 μm or less. preferable.

  It is also possible to stack a plurality of epitaxial growth substrates 103 and simultaneously slice a plurality of epitaxial growth substrates 103 stacked using a multi-wire saw having a plurality of wires or a multi-blade saw having a plurality of blades. . According to this method, since a plurality of epitaxial growth substrates 103 are sliced at the same time, productivity can be improved.

In the two-split slicing step, it is preferable that the region removed by slicing in the epitaxial growth substrate 103 is a region immediately above the seed substrate 101 of the epitaxial layer 102. This region has a relatively higher dislocation density than the upper and lower regions. As described above, in the GaN homoepitaxial growth, even if the seed substrate 101 having a relatively low dislocation density is used, the epitaxial growth by the current HVPE method is performed. In this case, the dislocation density increases to about 5 × 10 ⁸ / cm ² in the initial stage of growth, but the dislocation density decreases as the epitaxial growth proceeds, and the dislocation density is 5 × 10 ⁷ / cm ² or less when grown to about 400 to 800 μm. It becomes. Therefore, the dislocation density of the nitride semiconductor free-standing substrate obtained from the epitaxial layer 102 side is lowered by making the region where the dislocation density increases correspond to the region removed by the two-slice slice process and making this region the removal region. be able to. Furthermore, by doing in this way, it is possible to obtain a seed substrate having the same thickness as the original one after the two-division slice.

  In addition, by managing the displacement of the blade and wire during the two-slice process and reducing the local curvature (warp) of the slice surface, the subsequent device fabrication process can be stably advanced. In the present invention, since the epitaxial layer is grown on the same type of seed substrate by homoepitaxial growth, the warpage can be made extremely smaller than when the nitride semiconductor epitaxial layer is grown on the heterogeneous substrate by heteroepitaxial growth. The warp due to the displacement of the blade and wire during slicing remains, but the size can be controlled to 35 μm or less, particularly 20 μm or less even in the case of a 2-inch substrate (diameter 50 mm).

After the slicing step (step d), since there is a damaged layer on the slice surface of the slice substrate 104, this surface is wrapped to improve flatness and to make the slice substrate 104 have a predetermined thickness. . In this step, it is preferable to take a method of making the damaged layer shallow by gradually reducing the lapping abrasive grains of the slurry. Thereafter, the damaged substrate may be removed by etching the slice substrate 104 with hot KOH or the like (step e).
In the lapping step, polishing is performed by a polishing apparatus as shown in FIG. The surface of the slice substrate 104 opposite to the slice surface is adsorbed to the rotatable polishing head 41, and the slurry 45 is supplied to the polishing cloth 42 affixed on the rotatable surface plate 44 while supplying the slurry 45. The slicing surface is pressed and the polishing head 41 and the surface plate 44 are rotated together.
Thereafter, the surface on which epitaxial growth is performed, that is, the gallium surface ((0001) surface) side is used as a polishing surface, and polishing is performed by a polishing apparatus similar to that in the lapping process, for example, as shown in FIG. In this step, the pH of the slurry is adjusted and the damaged layer on the surface is removed by chemical mechanical polishing (step f).

Moreover, when the warpage of the seed substrate 101 is large, the warpage of the epitaxial growth substrate 103 after the epitaxial growth becomes large. In that case, as shown in FIG. 6, without correcting the warp, the wafer stage 32 is affixed to the wafer stage 32 and sliced, and then the slice surface side is pressure-bonded to the polishing head 41. Warping can be corrected by lapping as shown in FIG.
By performing the polishing as described above, the damaged layer on the slice surface is removed, and a nitride semiconductor free-standing substrate with high flatness can be obtained.
In addition to the above polishing, the damaged layer may be removed by various etchings.

The nitride semiconductor free-standing substrate 104 manufactured by the process as described above has a diameter equivalent to that of the seed substrate 101. In addition, since a new nitride semiconductor free-standing substrate is manufactured from the epitaxial layer 102 formed by homoepitaxial growth, the lattice constant of the epitaxial layer 102 is the same as that of the seed substrate 101, and the crystallinity of the seed substrate 101 is good. If an appropriate epitaxial pretreatment is performed, an epitaxial layer having a small strain and dislocation density can be grown to obtain a product nitride semiconductor free-standing substrate. When a threading dislocation density of 5 × 10 ⁷ / cm ² or less is used as the seed substrate 101, a threading dislocation density of the product nitride semiconductor free-standing substrate 104 is 5 × 10 ⁷ / cm ² or less. Thus, a nitride semiconductor free-standing substrate excellent as a substrate for device materials such as light emitting diodes, laser diodes, and electronic devices can be obtained. In the case where the threading dislocation density is used as a 1 × ¹⁰ 7 / cm ² or less as the seed substrate 101, as also the threading dislocation density as the product nitride semiconductor free-standing substrate 104 is 1 × ¹⁰ 7 / cm ² or less Can also be obtained.

  When a seed substrate 101 having a diameter of 37.5 mm (1.5 inches) or more is used, a product nitride semiconductor free-standing substrate 104 having a diameter of 37.5 mm or more can be obtained.

  In consideration of strength, resistance to deflection, etc., the product nitride semiconductor free-standing substrate 104 is preferably a nitride semiconductor free-standing substrate having a thickness of 250 μm or more. In order to obtain such a thickness, The thickness of the epitaxial layer 102 in the epitaxial growth step of the step b may be adjusted in consideration of the cutting margin in the slice in the two-division slicing step of d. For example, in the case of slicing using a multi-wire saw using a wire having a diameter of 200 μm in the two-division slicing step of step d, the cutting margin in the slice and the polishing margin of step e are estimated to be about 300 μm in total, and the epitaxial layer 102 The thickness may be 550 μm or more. However, as described above, the thickness of the epitaxial layer 102 is desirably 1 mm or less.

  The product nitride semiconductor free-standing substrate 104 can be sent to a device manufacturing process (for example, an MOCVD process for manufacturing an LED or an LD), but can also be used as a seed substrate for the process a. Since the nitride semiconductor free-standing substrate according to the present invention can be manufactured at a low cost as described above, the nitride semiconductor free-standing substrate 104 can be used again as a seed substrate to reduce the cost of the entire manufacturing cycle. Is preferable.

  Even in the conventional method of manufacturing a nitride semiconductor thick film epitaxial substrate on a heterogeneous substrate such as a sapphire substrate, a nitride semiconductor free-standing substrate can be manufactured by removing the initial substrate by laser lift-off or chemical etching, The initial board is consumed. On the other hand, in the method of manufacturing a nitride semiconductor free-standing substrate by homoepitaxial growth according to the present invention, the initial seed substrate 101 side can be used after two-division slicing.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

Example 1
A GaN free-standing substrate was manufactured by the method shown in FIG. 1 as follows.
As the seed substrate 101, a GaN free-standing substrate having a diameter of 50.8 mm (2 inches) and a thickness of 400 μm and having a dislocation density of 1 × 10 ⁷ / cm ² or less with a (0001) gallium surface polished to the quality for epitaxial growth is 8 A sheet was prepared (step a).

Next, using the epitaxial growth apparatus 1 as shown in FIG. 2, GaN was epitaxially grown as follows (step b).
Within the vertical chamber (quartz reaction tube) 2 having an inner diameter of 200 mm, eight seed substrates were placed on the susceptor 13 with the (0001) gallium surface facing up (step a). Further, a gallium chloride production tube 8 containing 400 g of metal gallium was provided in a gallium source boat 6 provided with a partition having a spacing of 1 cm. The gallium chloride production tube 8 was heated to 800 ° C. by the first heater 7, and the periphery of the seed substrate 101 placed on the susceptor 13 was heated to 1030 ° C. by the second heater 9. Hydrogen chloride was introduced into the gallium chloride production pipe 8 from the hydrogen chloride introduction pipe 4 using nitrogen as a carrier gas at a flow rate of 150 ml / min for hydrogen chloride and 500 ml / min for hydrogen. Further, nitrogen was introduced from the dilution gas introduction tube 5 and sprayed from the four gallium chloride blowing tubes 11 having an inner diameter of 8 mm toward the seed substrate 101 on the susceptor 13 at a linear velocity of about 30 cm / second.

From the ammonia introduction pipe 3, ammonia was introduced together with nitrogen in the same direction as the supply direction of the gallium chloride gas to the seed substrate 101. The total pressure in the reaction tube during growth was 100 kPa (1.0 atm), the partial pressure of ammonia was 25 kPa (0.25 atm), and the partial pressure of gallium chloride was 0.5 kPa.
Note that on the seed substrate 101, only nitrogen gas was initially supplied and then ammonia gas was supplied, and after the surface was stabilized, gallium chloride was supplied to start epitaxial growth.

As the susceptor 13, a carbon substrate coated with silicon carbide to a thickness of 100 μm was used. The susceptor 13 was rotated at a rotational speed of 10 rpm, and GaN was epitaxially grown on the seed substrate 101 for 10 hours. Of the obtained epitaxial growth substrate 103, the growth thickness of the epitaxial layer 102 was 850 μm. Polycrystalline deposition did not occur on the periphery and the back surface of the susceptor 13, and the substrate did not crack. The uniformity of the thickness of the epitaxial growth substrate 103 was within ± 5%, and the dislocation density on the surface was 1 × 10 ⁷ / cm ² .

Next, the center position of the chamfering was determined based on the back surface of the seed substrate 101, and W-shaped chamfering as shown in FIG. 3B was performed using a # 1200 diamond grindstone (step c).
The flat portion of the chamfered portion was divided into two slices with an inner peripheral blade, and thus the thickness of the blade was set to 500 μm, which was 250 μm plus the blade thickness of 250 μm.

Next, as shown in FIG. 4, the epitaxial growth substrate 103 was attached to the ingot holder 31 via the wafer stage 32, and the slice was divided into two by the inner peripheral blade blade 34 electrodeposited with diamond (step d). . Since the epitaxial growth substrate 103 was warped by about 40 to 50 μm, the epitaxial growth substrate 103 was adhered to the wafer stage 32 using a wax 38 without applying a load. Further, in order to prevent the substrate from cracking in the latter half of the slice, a contact plate 35 was bonded to each epitaxial growth substrate. Slicing was performed at a cutting speed of 0.2 mm / min while supplying cutting coolant.
In this case, the cutting allowance in the slice was about 300 μm. The thickness of the product GaN free-standing substrate after slicing was within about ± 40 μm with respect to the target center thickness. The patch plate 35 was removed after slicing.

  The shape of the chamfered portion of the slice substrate 104 after slicing is a shape as shown in FIG. 3C and is not symmetrical, but it is sufficient for preventing cracks and chipping in later steps. Was recognized.

Next, both surfaces of the slice substrate 104 were polished as follows to remove the damaged layer (step e), and the gallium surface was in a mirror state (step f).
The slice surface of the slice substrate 104 is bonded to the polishing head 41, and first, lapping (coarse wrap) is performed at a load of 1.0 kg / cm ² using a diamond slurry having a particle diameter of 15 μm to improve the flatness of the slice substrate 104. It was. Next, lapping (fine wrapping) was performed with a load of 2.0 kg / cm ² using a diamond slurry having a particle diameter of 6 μm. Thereafter, the slice substrate 104 obtained from the epitaxial layer side was etched with KOH. The slice substrate 104 on which the fine lapping was performed was washed, and the gallium surface side was mirror-polished with a load of 2.0 kg / cm ² using a diamond slurry having a particle diameter of 0.1 μm and a suede type polishing cloth. Further, in order to remove latent scratches and crystal distortion left on the sliced surface, the surface layer was etched by reactive ion etching (RIE) after cleaning. A slice substrate was placed on a silicon wafer on which a thick oxide film was formed in a commercially available apparatus, and etching was performed under a condition of 250 W using chlorine gas based on helium.

By the above method, 16 GaN free-standing substrates that were twice as many as the prepared 8 substrates could be obtained. All of the GaN free-standing substrates were substantially circular with a diameter of 50.8 mm, the thickness was about 400 μm, and the warp value was 25 μm or less. Also, the dislocation density on the surface is 5 × 10 ⁷ / cm ² or less, and the full width at half maximum (FWHM) in the X-ray rocking curve measurement is in the range of 170 to 260 arcsec, which is very high quality. It was.

(Example 2)
Of the 16 substrates obtained in Example 1, eight GaN free-standing substrates were used again as seed substrates 101, and GaN free-standing substrates were manufactured as follows.

As described above, the eight seed substrates 101 were GaN free-standing substrates having a diameter of 50.8 mm, a thickness of about 400 μm, a warp value of 25 μm or less, and a threading dislocation density of 5 × 10 ⁷ / cm ² or less ( Step a).
Next, growth was performed using the HPVE apparatus 1 as in Example 1, except that the growth time was 7 hours 30 minutes (step b). The thickness of the epitaxial layer 102 was 610 μm.
Next, a chamfering process (process c) was performed on the epitaxial growth substrate 103 in the same manner as in Example 1.

Next, a backing plate 35 was attached to the orientation flat portion of the chamfered epitaxial growth substrate 103 and placed on a wire saw wafer stage 32 as shown in FIG. The position of the wafer stage 32 was set by slicing the silicon wafer before slicing the epitaxial growth substrate 103 and confirming that the wafer on the wafer stage 32 side was sliced to a predetermined thickness in parallel.
In slicing the epitaxial growth substrate 103, the seed substrate 101 side was pressure bonded to the wafer stage 32. The wire used was a 130 μm diameter wire electrodeposited with 20 μm diamond. Slicing was performed at a work feed speed of 2 mm / hour (step d). After the epitaxial growth substrate 103 was sliced into two parts, the contact plate 35 was removed. The thickness of the slice substrate on the wafer stage 32 side (the slice substrate obtained from the epitaxial layer 102 side) was 420 ± 10 μm, and the cutting margin at this time was about 160 μm. After slicing, the slice surface side was chamfered.

Next, in the same manner as in Example 1, the slice substrate 104 was subjected to rough wrapping and fine wrapping, and then etched with KOH. However, in this example, since the thickness variation of the slice substrate was small, the load of the rough lap was set at 2.0 kg / cm ² and the polishing time was shortened. Thereafter, the slice substrate 104 is sufficiently washed, mirror polished with 0.1 μm diamond abrasive grains, and the slice substrate 104 is peeled off from the polishing head, and then sufficiently washed, and subjected to RIE under the same conditions as in Example 1. Polishing strain was removed. Thereafter, cleaning was performed again to obtain 16 new product GaN free-standing substrates. The dimensions and crystal quality of this GaN free-standing substrate were the same as in Example 1.

(Example 3)
Similarly to Example 1, the epitaxial layer was simultaneously grown by 1 mm (= 1000 μm) on three seed substrates 101 having a threading dislocation density of 1 × 10 ⁷ / cm ² , and the process up to manufacturing the epitaxial growth substrate 103 was performed. Three epitaxial growth substrates 103 were obliquely polished and etched with a high-temperature potassium hydroxide solution, and the density distribution of etch pits (dislocation pits) in the depth direction was examined. FIG. 9 is a graph showing the relationship between the epitaxial layer thickness and the etch pit density. The epitaxial layer thickness of 0 μm is the interface with the seed substrate 101 side. The dislocation density increases by an order of magnitude or more than the dislocation density of the substrate in the initial stage of epitaxial growth, but gradually decreases toward the epitaxial surface and approaches the dislocation density of the seed substrate 101 at a stage where the epitaxial growth is performed by about 400 to 800 μm. It became. Since the portion of the epitaxial layer thickness of about 0 to 300 μm whose dislocation density is significantly higher than that of the seed substrate 101 is removed by the two-slice process, the crystal quality of the product GaN free-standing substrate 104 obtained from the epitaxial layer 102 side is also improved. It turns out that it becomes a thing equivalent to 101. However, when the epitaxial growth was performed to a thickness exceeding 1 mm, the uniformity of the surface gradually deteriorated and protrusions were generated.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  For example, in the above embodiment, the case where the nitride semiconductor is GaN which is a gallium nitride is mainly described, but the present invention can be applied to any group III nitride semiconductor.

It is the flow sheet which showed the manufacturing process of the nitride semiconductor self-supporting substrate concerning the present invention. It is a schematic block diagram which shows an example of the vertical HVPE epitaxial apparatus which can be used for this invention. In the manufacturing method of the nitride semiconductor self-supporting substrate according to the present invention, a schematic cross-sectional view of the substrate before and after the two-division slice after epitaxial growth is shown, (a) is a peripheral portion of the epitaxial growth substrate before the two-division slice process (B) is a schematic cross-sectional view showing the shape of chamfering applied to the peripheral portion of the epitaxial growth substrate before the 2-division slice, and (c) is a view after the 2-division slice is obtained. It is a schematic sectional drawing which shows the peripheral part of a slice board | substrate. It is outline explanatory drawing which showed the mode at the time of performing a 2 division | segmentation slice using an internal peripheral blade with an epitaxial growth board | substrate. It is outline | summary explanatory drawing which showed the mode at the time of performing a 2 division | segmentation slice using a wire saw on an epitaxial growth board | substrate. It is the schematic sectional drawing which showed the mode of adhesion | attachment of the epitaxial growth board | substrate to a wafer chuck when there exists curvature in an epitaxial growth board | substrate. It is the schematic which shows the mode of the mechanical polishing (chemical mechanical polishing) which can be performed after a 2 division | segmentation slice process. It is the schematic which shows the mode of the mechanical polishing which can be performed after a 2 division | segmentation slice process, (a) is a case where a slice surface becomes concave at the time of 2 division | segmentation slice, (b) is a slice surface at the time of 2 division | segmentation slice This is the case where becomes convex. 6 is a graph showing the relationship between the epitaxial layer thickness of the epitaxially grown substrate and the etch pit density in Example 3.

Explanation of symbols

101 ... Seed substrate, 102 ... Epitaxial layer,
103 ... epitaxial growth substrate, 103a ... chamfered portion, 103b ... groove,
104 ... (Product) Nitride semiconductor free-standing substrate (slice substrate),
DESCRIPTION OF SYMBOLS 1 ... Epitaxial growth apparatus (HVPE apparatus), 2 ... Vertical reaction tube (chamber),
3 ... Ammonia introduction pipe, 4 ... Reaction gas (hydrogen chloride) introduction pipe,
5 ... Gas introduction pipe for dilution,
6 ... Raw material group III metal (gallium) boat, 7 ... First heater,
8 ... Group III metal compound (gallium chloride) production tube, 9 ... Second heater,
10 ... Rectifying plate, 11 ... Group III metal compound (gallium chloride) blowing tube,
13 ... Susceptor, 14 ... Internal protective pipe, 15 ... Gas exhaust pipe,
31 ... Ingot holder, 32 ... Wafer stage, 34 ... Inner blade,
35 ... Watt plate, 36 ... Cutting coolant supply means, 38 ... Wax,
41 ... Polishing head, 42 ... Polishing cloth, 44 ... Surface plate, 45 ... Slurry,
51 ... Wire saw.

Claims (10)

at least,
Preparing eight or more nitride semiconductor free-standing substrates to be seed substrates;
By the HVPE method using a vertical type HVPE apparatus, a nitride semiconductor of the same type as the seed substrate is applied to the eight or more seed substrates on the eight or more seed substrates in the same chamber. A process of epitaxial growth at the same time ;
Slicing the epitaxially grown substrate that has undergone the epitaxial growth in parallel with the epitaxial growth surface and dividing it into two to produce two nitride semiconductor free-standing substrates from one seed substrate Manufacturing method of semiconductor free-standing substrate.   The method for manufacturing a nitride semiconductor free-standing substrate according to claim 1, wherein the nitride semiconductor free-standing substrate manufactured by the method for manufacturing a nitride semiconductor free-standing substrate according to claim 1 is used again as the seed substrate. Method for manufacturing a nitride semiconductor free-standing substrate according to claim 1 or claim 2, characterized in that polishing the slice plane of the slice to bisected epitaxial growth substrate. Method for manufacturing a nitride semiconductor free-standing substrate according to any one of claims 1 to 3, characterized in that the thickness of the epitaxial layer and 1mm or less to form in the epitaxial growth step. The nitride semiconductor free-standing substrate according to any one of claims 1 to 4 , wherein the nitride semiconductor free-standing substrate serving as the seed substrate and the nitride semiconductor free-standing substrate to be manufactured are GaN free-standing substrates. Manufacturing method. The nitride semiconductor free-standing substrate serving as the seed substrate has a diameter of 37.5 mm or more, a thickness of 250 µm or more, and a warp value of 35 µm or less. The method for producing a nitride semiconductor free-standing substrate according to any one of claims 5 to 6. Nitriding according the nitride semiconductor free-standing substrate serving as the seed substrate, in any one of claims 1 to 6, characterized in that as the threading dislocation density of 5 × 10 7 ^/ cm ² or less Method for manufacturing a self-supporting semiconductor substrate. After it said epitaxial growth step, the slice before the step, the epitaxial growth according to claim 1 to claim 7, characterized in that a groove for guiding a tool for both slicing perform chamfering the peripheral portion of the substrate A method for producing a nitride semiconductor free-standing substrate according to any one of the above. The slicing step is performed using an inner peripheral blade with a blade thickness of 250 μm or less, a single wire saw with a wire diameter of 200 μm or less, or a single blade saw with a blade thickness of 250 μm or less. A method for manufacturing a nitride semiconductor free-standing substrate according to any one of claims 1 to 8 . In the slicing step, a plurality of the epitaxial growth substrates are stacked, and a plurality of the epitaxial growth substrates stacked using a multi-wire saw having a wire diameter of 200 μm or less, or a multi-blade saw having a blade thickness of 250 μm or less are simultaneously formed. The method for manufacturing a nitride semiconductor free-standing substrate according to any one of claims 1 to 8 , wherein the method is performed by slicing.

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